First of all, you can of course submit your papers to regular conferences/workshops. Usually, you can have the choice between regular papers, short papers or posters (the last two categories are sometimes merged). You need to be careful whether the accepted papers will be published in the proceedings (sometimes short papers/posters are not), otherwise it might not count as a publication for your course.
Some conferences also organize a doctoral symposium, which is reserved for PhD students. It can be a good opportunity to attend a selective conference, and to do some networking with other students.
In order to know which conferences are the most suitable for you, the better option is to ask your advisors, they should know about that. You can also search on the web for "call for papers" with some keywords corresponding to your research field.